It's been there since volume 1, since Ichi saw her on a magazine and told himself "everything is pointless and stupid". BokuYaba was born from Norio thinking about what it would be like to date an idol, so this was gonna happen sooner or later.
Holy shit, finally someone did it
The last time I read this, I was a teenager, though... I'm an adult now, so when I find/reread these age gap romances i used to love...
(Psst! I see dead people)